The references cited in the present application are not admitted to be prior art to the claimed invention.
It is estimated that about 3% of the world's population are infected with the Hepatitis C virus (HCV). (Wasley, et al. 2000. Semin. Liver Dis. 20, 1-16.) Exposure to HCV results in an overt acute disease in a small percentage of cases, while in most instances the virus establishes a chronic infection causing liver inflammation and slowly progresses into liver failure and cirrhosis. (Iwarson, 1994. FEMS Microbiol. Rev. 14, 201-204.) In addition, epidemiological surveys indicate an important role of HCV in the pathogenesis of hepatocellular carcinoma. (Kew, 1994. FEMS Microbiol. Rev. 14, 211-220, Alter, 1995. Blood 85, 1681-1695.)
The HCV genome consists of a single strand RNA of about 9.5 kb in length, encoding a precursor polyprotein of about 3000 amino acids. (Choo, et al., 1989. Science 244, 362-364, Choo, et al., 1989. Science 244, 359-362, Takamizawa, et al., 1991. J. Virol. 65, 1105-1113.) The HCV polyprotein contains the viral proteins in the order: C-E1-E2-p7-NS2-NS3-NS4A-NS4B-NS5A-NS5B.
Individual viral proteins are produced by proteolysis of the HCV polyprotein. Host cell proteases release the putative structural proteins C, E1, E2, and p7, and create the N-terminus of NS2 at amino acid 810. (Mizushima, et al., 1994. J. Virol. 68, 2731-2734, Hijikata, et al., 1993. P.N.A.S. USA 90, 10773-10777.)
The non-structural proteins NS3, NS4A, NS4B, NS5A and NS5B presumably form the virus replication machinery and are released from the polyprotein. A zinc-dependent protease associated with NS2 and the N-terminus of NS3 is responsible for cleavage between NS2 and NS3. (Grakoui, et al, 1993. J. Virol. 67, 1385-1395, Hijikata, et al., 1993. P.N.A.S. USA 90, 10773-10777.) A distinct serine protease located in the N-terminal domain of NS3 is responsible for proteolytic cleavages at the NS3/NS4A, NS4A/NS4B, NS4B/NS5A and NS5A/NS5B junctions. (Barthenschlager, et al., 1993. J. Virol. 67, 3835-3844, Grakoui, et al., 1993. Proc. Natl. Acad. Sci. USA 90, 10583-10587, Tomei, et al., 1993. J. Virol. 67, 4017-4026.) NS4A provides a cofactor for NS3 activity. (Failla, et al., J. Virol. 1994. 68, 3753-3760, De Francesco, et al., U.S. Pat. No. 5,739,002.) NS5A is a highly phosphorylated protein concurring interferon resistance. (De Francesco, et al., 2000. Semin Liver Dis., 20(1), 69-83, Pawlotsky, 1999. J. Viral Hepat. Suppl. 1, 47-48.) NS5B provides an RNA polymerase. (De Francesco, et al., International Publication Number WO 96/37619, Behrens, et al., 1996. EMBO 15, 12-22, Lohmann, et al., 1998. Virology 249, 108-118.)
Lohmann, et al., Science 285, 110-113, 1999, illustrates the ability of a biscistronic HCV replicon to replicate in a hepatoma cell line. The biscistonic HCV replicon contained a neomycin cistron and an NS2-NS5B or an NS3-NS5B cistron. “NS2-NS5B” refers to a NS2-NS3-NS4A-NS4B-NS5A-NS5B polyprotein. “NS3NS5B” refers to a NS3-NS4A-NS4B-NS5A-NS5B polyprotein.
Bartenschlager, European Patent Application 1 043 399, published Oct. 11, 2000 (not admitted to be prior art to the claimed invention), describes a cell culture system for autonomous HCV RNA replication and protein expression. Replication and protein expression is indicated to occur in sufficiently large amounts for quantitative determination. European Patent Application 1 043 399 indicates that prior cell lines or primary cell cultures infected with HCV do not provide favorable circumstances for detecting HCV replication.